Tympanic Membrane Vibrations in Cats Studied by Time-Averaged Holography

Khanna, Shyam M.; Tonndorf, Juergen

doi:10.1121/1.1913050

Cited by 190 publications

(113 citation statements)

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“…Our single model has been able to show both a smoothly varying middle-ear pressure transfer function (24) and the highly nonuniform displacement patterns seen experimentally (23,25) for frequencies up to 20 kHz. For frequencies Ͻ3 kHz, the eardrum surface moves together in unison (Fig.…”

Section: Resultsmentioning

confidence: 96%

The discordant eardrum

Fay¹,

Puria

Steele³

2006

Proc. Natl. Acad. Sci. U.S.A.

125

141

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At frequencies above 3 kHz, the tympanic membrane vibrates chaotically. By having many resonances, the eardrum can transmit the broadest possible bandwidth of sound with optimal sensitivity. In essence, the eardrum works best through discord. The eardrum's success as an instrument of hearing can be directly explained through a combination of its shape, angular placement, and composition. The eardrum has a conical asymmetrical shape, lies at a steep angle with respect to the ear canal, and has organized radial and circumferential collagen fiber layers that provide the scaffolding. Understanding the role of each feature in hearing transduction will help direct future surgical reconstructions, lead to improved microphone and loudspeaker designs, and provide a basis for understanding the different tympanic membrane structures across species. To analyze the significance of each anatomical feature, a computer simulation of the ear canal, eardrum, and ossicles was developed. It is shown that a cone-shaped eardrum can transfer more force to the ossicles than a flat eardrum, especially at high frequencies. The tilted eardrum within the ear canal allows it to have a larger area for the same canal size, which increases sound transmission to the cochlea. The asymmetric eardrum with collagen fibers achieves optimal transmission at high frequencies by creating a multitude of deliberately mistuned resonances. The resonances are summed at the malleus attachment to produce a smooth transfer of pressure across all frequencies. In each case, the peculiar properties of the eardrum are directly responsible for the optimal sensitivity of this discordant drum.collagen fibers ͉ hearing sensitivity ͉ middle ear ͉ transducers T he function of the middle ear in terrestrial mammals is to transfer acoustic energy between the air of the ear canal to the fluid of the inner ear. The first and crucial step of the transduction process takes place at the tympanic membrane, which converts sound pressure in the ear canal into vibrations of the middle ear bones. Understanding how the tympanic membrane manages this task so successfully over such a broad range of frequencies has been a subject of research since Helmholtz's publication in 1868 (1, 2).Even though the function of the eardrum is clear and the anatomy of the eardrum is well characterized, the connection between the anatomical features and the ability of the eardrum to transduce sound has been missing. The missing structurefunction relationships can be summarized by the following three questions. Why does the mammalian eardrum have its distinctive conical and toroidal shape? What is the advantage of its angular placement in the ear canal? What is the significance of its highly organized radial and circumferential fibers?The shape of the human and feline eardrum is known from detailed Moiré interferometry contour maps (refs. 3 and 4 and Fig. 1a). From the contour maps, three-dimensional reconstructions reveal the striking similarity of the two eardrums. In both cases, the eardrum has an ell...

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Section: Resultsmentioning

confidence: 96%

The discordant eardrum

Fay¹,

Puria

Steele³

2006

Proc. Natl. Acad. Sci. U.S.A.

125

141

View full text Add to dashboard Cite

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“…Additionally, this arrangement causes the outward curved shape of the tympanic membrane and provides the cante lever first proposed by Helmholtz [15,16]. It is difficult to reconstruct this sophisticated design and post operative the acoustic characteristics of tympanic membrane may change [17].…”

Section: Discussionmentioning

confidence: 99%

Cartilage–Perichondrium: An Ideal Graft Material?

Chhapola¹,

Matta²

2011

Indian J Otolaryngol Head Neck Surg

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Temporalis fascia has long been regarded as the ideal graft material for tympanic membrane repair. However it often does not seem to withstand negative middle ear pressure in the post operative period. Tragal cartilage with perichondrium would appear to be a better graft material with good hearing outcome. It can be obtained easily with cosmetically acceptable incision. In the present study, we have compared the graft properties of temporalis fascia verses tragal cartilage perichondrium with respect to healing, hearing and rate of post operative retraction or reperforation. 132 patients of chronic otitis media with pure conductive hearing loss were posted for tympanoplasty. Temporalis fascia graft was used in 71 patients and cartilage perichondrium (composite graft) was used in 61 patients. Post operative healing, hearing and rate of retraction or reperforation was compared for both the graft materials. All the patients were followed up for 2 years. Patients where temporalis fascia graft was used, 60 (84.5%) showed a good neotympanum, 7(9.85%) had reperforation and 5(7.04%) had retraction pockets. Patients where tragal cartilage perichondrium was used, 60(98.36%) showed a healed tympanic membrane and only 1(1.63%) had reperforation. None of the patients showed retraction pocket or cholestetoma. Postoperative hearing was accessed 6 months after surgery. Patients with temporalis fascia graft showed an air bone gap of less than 10 dB in 49 (82%) patients and more than 10 dB in 11 (18%) patients. Air bone gap closure with tragal cartilage perichondrium was less than 10 dB in 45 (78%) patients and more than 10 dB in 13 patients (22%). Tragal cartilage perichondrium (\0.5 mm) seems to be an ideal graft material for tympanic membrane in terms of postoperative healing and acoustic properties. It can easily withstand negative middle ear pressure which may have contributed to the development of otitis media and significantly affect healing outcomes in postoperative period. Tragal cartilage being composed of collagen type II is also physiologically similar to the nature of the tympanic membrane.

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“…Tonndorf and Khanna (1972) and Khanna and Tonndorf (1972) were the first to study vibration patterns of the human and cat TM by time-averaged laser holography, at frequencies up to 5 and 6 kHz, respectively. They observed that, in both species, the maximum displacement happens in the posterior region, and for frequencies beyond 2.5 kHz, the simple low-frequency vibration pattern starts to break up and vibration patterns become more complex.…”

Section: Introductionmentioning

confidence: 99%

Experimental Study of Vibrations of Gerbil Tympanic Membrane with Closed Middle Ear Cavity

Maftoon

Funnell

Daniel

et al. 2013

JARO

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The purpose of the present work is to investigate the spatial vibration pattern of the gerbil tympanic membrane (TM) as a function of frequency. In vivo vibration measurements were done at several locations on the pars flaccida and pars tensa, and along the manubrium, on surgically exposed gerbil TMs with closed middle ear cavities. A laser Doppler vibrometer was used to measure motions in response to audio frequency sine sweeps in the ear canal. Data are presented for two different pars flaccida conditions: naturally flat and retracted into the middle ear cavity. Resonance of the flat pars flaccida causes a minimum and a shallow maximum in the displacement magnitude of the manubrium and pars tensa at low frequencies. Compared with a flat pars flaccida, a retracted pars flaccida has much lower displacement magnitudes at low frequencies and does not affect the responses of the other points. All manubrial and pars tensa points show a broad resonance in the range of 1.6 to 2 kHz. Above this resonance, the displacement magnitudes of manubrial points, including the umbo, roll off with substantial irregularities. The manubrial points show an increasing displacement magnitude from the lateral process toward the umbo. Above 5 kHz, phase differences between points along the manubrium start to become more evident, which may indicate flexing of the tip of the manubrium or a change in the vibration mode of the malleus. At low frequencies, points on the posterior side of the pars tensa tend to show larger displacements than those on the anterior side. The simple low-frequency vibration pattern of the pars tensa becomes more complex at higher frequencies, with the breakup occurring at between 1.8 and 2.8 kHz. These observations will be important for the development and validation of middle ear finite-element models for the gerbil.

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Tympanic Membrane Vibrations in Cats Studied by Time-Averaged Holography

Cited by 190 publications

References 0 publications

The discordant eardrum

The discordant eardrum

Cartilage–Perichondrium: An Ideal Graft Material?

Experimental Study of Vibrations of Gerbil Tympanic Membrane with Closed Middle Ear Cavity

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